Valve timing adjustment device

ABSTRACT

A valve timing adjustment device includes: a center bolt being bottomed cylindrical; a spool disposed in a hollow portion of the center bolt so as to be linearly movable; an oil supply path including a region that is formed inside a cylindrical wall of the center bolt and along the longitudinal direction of the center bolt; a first annular groove formed on the inner periphery of the center bolt and communicating with the oil supply path; and a second annular groove formed on the outer periphery of the spool, disposed to face the first annular groove, and communicating with the oil supply path via the first annular groove. The oil supply path is capable of selectively, communicating with either a first work port or a second work port via the first annular groove and the second annular groove depending on the position of the spool that is linearly moving.

TECHNICAL FIELD

The present invention relates to a valve timing adjustment device.

BACKGROUND ART

Conventionally, valve timing adjustment devices for variable valve timing mechanisms (hereinafter referred to as “VVT”) have been developed (see Patent Literature 1, for example).

CITATION LIST Patent Literatures

-   Patent Literature 1: JP 2015-161232 A

SUMMARY OF INVENTION Technical Problem

A conventional valve timing adjustment device includes a center bolt and a spool. The center bolt is in a substantially cylindrical and bottomed shape. The substantially cylindrical and bottomed shape may be hereinafter simply referred to as “bottomed cylindrical”. The spool is disposed in a hollow portion of the center bolt. The spool is disposed to be linearly movable with respect to the center bolt. The center bolt and the spool share an axial center. The axial direction with respect to the axial center may be hereinafter simply referred to as an “axial direction”.

The center bolt in a conventional valve timing adjustment device has three types of ports. Specifically, the center bolt in a conventional valve timing adjustment device includes a port for supplying oil (hereinafter referred to as a “supply port”), a port for communicating with an advance chamber (hereinafter referred to as an “advance port”), and a port for communicating with a retard chamber (hereinafter referred to as a “retard port”). The three types of ports are arranged in sequence along the axial direction. For example, these ports are arranged in sequence in the order of the advance port, the supply port, and the retard port.

Here, from the viewpoint of reducing the size (hereinafter referred to as being “made thinner”) of the valve timing adjustment device with respect to the axial direction, it is desired that the number of arranged ports with respect to the axial direction is reduced.

The present invention has been made in order to solve the problem as described above, and an object of the present invention is to reduce the number of arranged ports with respect to the axial direction.

Solution to Problem

A valve timing adjustment device of the present invention includes: a center bolt being bottomed cylindrical; a spool disposed in a hollow portion of the center bolt so as to be linearly movable; an oil supply path including a region that is formed inside a cylindrical wall of the center bolt and along a longitudinal direction of the center bolt; a first annular groove formed on the inner periphery of the center bolt and communicating with the oil supply path; and a second annular groove formed on the outer periphery of the spool, disposed to face the first annular groove, and communicating with the oil supply path via the first annular groove, in which the oil supply path is capable of selectively communicating with either a first work port or a second work port via the first annular groove and the second annular groove depending on the position of the spool that is linearly moving.

Advantageous Effects of Invention

According to the present invention, the configuration described above makes it possible to eliminate the need for a port equivalent to the supply port. As a result, the number of arranged ports with respect to the axial direction can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram illustrating a main part of a valve timing adjustment device according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a main part of a valve timing adjustment device for comparison with the valve timing adjustment device according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a main part of a valve timing adjustment device according to a second embodiment.

DESCRIPTION OF EMBODIMENTS

In order to explain the present invention in more detail, embodiments of the present invention will now be described with reference to the accompanying drawings.

First Embodiment

FIG. 1 is an explanatory diagram illustrating a main part of a valve timing adjustment device according to a first embodiment. Referring to FIG. 1, the following describes the valve timing adjustment device according to the first embodiment.

As illustrated in FIG. 1, an end portion of a camshaft 1, a center bolt 2, a spool 3, and a rotor 4 form the main part of a valve timing adjustment device 100.

The rotor 4 is in a substantially cylindrical shape. The center bolt 2 is disposed in a hollow portion of the rotor 4. The center bolt 2 is in a substantially cylindrical and bottomed shape. The spool 3 is disposed in a hollow portion of the center bolt 2. The center bolt 2 is fastened to the camshaft 1. The camshaft 1, the center bolt 2, the spool 3, and the rotor 4 share an axial center A. An axial direction with respect to the axial center A is hereinafter simply referred to as an “axial direction”. A radial direction with respect to the axial center A is simply referred to as a “radial direction”. A circumferential direction with respect to the axial center A is simply referred to as a “circumferential direction”.

A male screw (not illustrated) is formed on the outer periphery of an end portion of the center bolt 2. On the other hand, a recess 11 is formed in the end portion of the camshaft 1, and a female screw (not illustrated) is formed on the inner periphery of the recess 11. The male screw is screwed with the female screw, whereby the center bolt 2 is fastened to the camshaft 1. The recess 11 forms a space S.

The center bolt 2 includes a flange 21. The rotor 4 is held between the flange 21 and the end portion of the camshaft 1. In the figure, CS_1 indicates a surface of the flange 21, the surface being in contact with the rotor 4, that is, a surface of the rotor 4, the surface being in contact with the flange 21. In addition, CS_2 indicates a surface of the end portion of the camshaft 1, the surface being in contact with the rotor 4, that is, a surface of the rotor 4, the surface being in contact with the end portion of the camshaft 1. The surfaces CS_1 and CS_2 are hereinafter each referred to as a “contact surface”.

The spool 3 is disposed to be linearly movable with respect to the center bolt 2. In the figure, D_1 indicates the linear movement direction of the spool 3. The rotor 4 is disposed to be rotatable together with the camshaft 1 and the center bolt 2.

Here, one or more through holes 12 are formed in the camshaft 1, and one or more holes 22 are formed in a cylindrical wall of the center bolt 2. FIG. 1 illustrates one through hole 12 out of the one or more through holes 12 and one hole 22 out of the one or more holes 22. Each through hole 12 has a longitudinal direction along the radial direction. Each hole 22 has a longitudinal direction along the axial direction. Each through hole 12 communicates with the corresponding hole 22 via the space S. Each through hole 12, the space S, and the corresponding hole 22 form a main part of a path for oil supply (hereinafter referred to as an “oil supply path”) OSP.

A plurality of through holes 23_1 is formed in the cylindrical wall of the center bolt 2. The through holes 23_1 are arranged along the circumferential direction. FIG. 1 illustrates two through holes 23_1 out of the plurality of through holes 23_1. Each through hole 23_1 forms a port (hereinafter referred to as a “first work port”) WP_1 corresponding to either one of the advance port and the retard port.

An annular recess 41_1 is formed on the inner periphery of the rotor 4, and a plurality of through holes 42_1 is formed in the rotor 4. The through holes 42_1 are arranged along the circumferential direction. FIG. 1 illustrates one through hole 42_1 out of the plurality of through holes 42_1. Each through hole 42_1 has a longitudinal direction with respect to the radial direction. Each through hole 42_1 communicates with the corresponding one space out of a plurality of spaces each forming either one of an advance chamber and a retard chamber. In FIG. 1, illustration of the plurality of spaces is omitted.

Each through hole 23_1 communicates with the corresponding through hole 42_1 via the annular recess 41_1. Forming the annular recess 41_1 achieves the state in which each through hole 23_1 communicates with the corresponding through hole 42_1 regardless of the positional relationship between the center bolt 2 and the rotor 4 with respect to the rotation direction.

A plurality of through holes 23_2 is formed in the cylindrical wall of the center bolt 2. The through holes 23_2 are arranged along the circumferential direction. FIG. 1 illustrates one through hole 23_2 out of the plurality of through holes 23_2. Each through hole 23_2 forms a port (hereinafter referred to as a “second work port”) WP_2 corresponding to the other one of the advance port and the retard port.

An annular recess 41_2 is formed on the inner periphery of the rotor 4, and a plurality of through holes 42_2 is formed in the rotor 4. The through holes 42_2 are arranged along the circumferential direction. FIG. 1 illustrates one through hole 42_2 out of the plurality of through holes 42_2. Each through hole 42_2 has a longitudinal direction with respect to the radial direction. Each through hole 42_2 communicates with the corresponding one space out of a plurality of spaces each forming the other one of the advance chamber and the retard chamber. In FIG. 1, illustration of the plurality of spaces is omitted.

Each through hole 23_2 communicates with the corresponding through hole 42_2 via the annular recess 41_2. Forming the annular recess 41_2 achieves the state in which each through hole 23_2 communicates with the corresponding through hole 42_2 regardless of the positional relationship between the center bolt 2 and the rotor 4 with respect to the rotation direction.

The following mainly describes an example in which the first work port WP_1 corresponds to the advance port and the second work port WP_2 corresponds to the retard port. In other words, the following mainly describes an example in which each through hole 42_1 communicates with the corresponding one space out of the plurality of spaces each forming the advance chamber, and each through hole 42_2 communicates with the corresponding one space out of the plurality of spaces each forming the retard chamber.

An annular groove (hereinafter referred to as a “first annular groove”) 24 is formed on the inner periphery of the center bolt 2. An annular groove (hereinafter referred to as a “second annular groove”) 31 is formed on the outer periphery of the spool 3. The first annular groove 24 communicates with the oil supply path OSP. The second annular groove 31 is disposed to face the first annular groove 24.

The state in which the oil supply path OSP communicates with the first work port WP_1 via the first annular groove 24 and the second annular groove 31 in the valve timing adjustment device 100 is hereinafter referred to as a “first oil supply state”. In addition, the state in which the oil supply path OSP communicates with the second work port WP_2 via the first annular groove 24 and the second annular groove 31 in the valve timing adjustment device 100 is referred to as a “second oil supply state”.

The valve timing adjustment device 100 can be selectively set to either the first oil supply state or the second oil supply state depending on the position of the spool 3 that is linearly moving. In other words, the oil supply path OSP can selectively communicate with either the first work port WP_1 or the second work port WP_2 via the first annular groove 24 and the second annular groove 31 depending on the position of the spool 3 that is linearly moving. FIG. 1 illustrates the valve timing adjustment device 100 in the first oil supply state. Illustration of the valve timing adjustment device 100 in the second oil supply state is omitted.

The spool 3 has a hollow portion 32. The hollow portion 32 forms a main part of a path for discharging oil (hereinafter referred to as an “oil exit path”) OEP. One or more through holes (not illustrated) for discharging oil are formed at an end portion of the spool 3.

In the figure, SS indicates a surface of the outer periphery of the center bolt 2, the surface being in contact with the inner periphery of the rotor 4, that is, a surface of the inner periphery of the rotor 4, the surface being in contact with the outer periphery of the center bolt 2. The surface SS is hereinafter referred to as a “seal surface”. The seal surface SS is a region for suppressing the occurrence of oil leakage between the first work port WP_1 and the second work port WP_2. Accordingly, the seal surface SS is disposed between the first work port WP_1 and the second work port WP_2.

The main part of the valve timing adjustment device 100 is configured as described above.

The following describes operation of the valve timing adjustment device 100, focusing on the operation of supplying oil to the advance chamber. In other words, the following mainly describes the operation in the first oil supply state.

First, oil in an oil pan (not illustrated) is supplied to the oil supply path OSP by a pump (not illustrated). The supplied oil passes through each through hole 12, the space S, each hole 22, the first annular groove 24, and the second annular groove 31, and is supplied to the first work port WP 1. The supplied oil passes through each through hole 23_1, the annular recess 41_1, and each through hole 42_1, and is supplied to the advance chamber.

At the same time, at least part of oil in the retard chamber is unnecessary. The unnecessary oil passes through each through hole 42_2, the annular recess 41_2, each through hole 23_2, and the hollow portion 32, and is discharged to the oil pan. In other words, the unnecessary oil is discharged to the outside of the valve timing adjustment device 100 through the second work port WP_2 and the oil exit path OEP.

The following describes operation of the valve timing adjustment device 100, focusing on the operation of supplying oil to the retard chamber. In other words, the following mainly describes the operation in the second oil supply state.

First, oil in the oil pan is supplied to the oil supply path OSP by the pump. The supplied oil passes through each through hole 12, the space S, each hole 22, the first annular groove 24, and the second annular groove 31, and is supplied to the second work port WP_2. The supplied oil passes through each through hole 23_2, the annular recess 41_2, and each through hole 42_2, and is supplied to the retard chamber.

At the same time, at least part of oil in the advance chamber is unnecessary. The unnecessary oil passes through each through hole 42_1, the annular recess 41_1, each through hole 23_1, and the hollow portion 32, and is discharged to the oil pan. In other words, the unnecessary oil is discharged to the outside of the valve timing adjustment device 100 through the first work port WP_1 and the oil exit path OEP.

Referring to FIG. 2, the following describes a valve timing adjustment device 200 for comparison with the valve timing adjustment device 100.

As illustrated in FIG. 2, an end portion of a camshaft 5, a center bolt 6, a spool 7, and a rotor 8 form a main part of a valve timing adjustment device 200. The camshaft 5, the center bolt 6, the spool 7, and the rotor 8 correspond to the camshaft 1, the center bolt 2, the spool 3, and the rotor 4, respectively.

Accordingly, the camshaft 5, the center bolt 6, the spool 7, and the rotor 8 share an axial center A′. In the figure, D′_1 indicates the linear movement direction of the spool 7. In the figure, CS′_1 indicates a contact surface of the rotor 8, the contact surface being in contact with a flange 61 of the center bolt 6, that is, a contact surface of the flange 61 of the center bolt 6, the contact surface being in contact with the rotor 8. In the figure, CS′_2 indicates a contact surface of the end portion of the camshaft 5, the contact surface being in contact with the rotor 8, that is, a contact surface of the rotor 8, the contact surface being in contact with the end portion of the camshaft 5. A recess 51 in the end portion of the camshaft 5 forms a space S′.

Here, one or more holes 52 are formed in the camshaft 5, one or more holes 53 are formed in the camshaft 5, one or more holes 81 are formed in the rotor 8, and one or more through holes 82 are formed in the rotor 8. FIG. 2 illustrates one hole 52 out of the one or more holes 52, one hole 53 out of the one or more holes 53, one hole 81 out of the one or more holes 81, and one through hole 82 out of the one or more through holes 82. Each hole 52 has a longitudinal direction along the radial direction. Each hole 53 has a longitudinal direction along the axial direction. Each hole 81 has a longitudinal direction along the axial direction. Each through hole 82 has a longitudinal direction along the radial direction.

Each hole 52 communicates with the corresponding one through hole 82 out of the one or more through holes 82 via the corresponding one hole 53 out of the one or more holes 53 and via the corresponding one hole 81 out of the one or more holes 81. Each hole 52, the corresponding hole 53, the corresponding hole 81, and the corresponding through hole 82 form a main part of the oil supply path OSP′.

An annular groove 83 is formed on the inner periphery of the rotor 8, and one or more through holes 62 are formed in a cylindrical wall of the center bolt 6. The one or more through holes 62 are arranged along the circumferential direction. In FIG. 2, two or more through holes 62 are formed in the cylindrical wall of the center bolt 6, and two through holes 62 out of the two or more through holes 62 are illustrated. Each through hole 62 communicates with the corresponding through hole 82 via the annular groove 83. Each through hole 62 forms a supply port SP.

A plurality of through holes 63_1 is formed in the cylindrical wall of the center bolt 6. The through holes 63_1 are arranged along the circumferential direction. FIG. 2 illustrates two through holes 63_1 out of the plurality of through holes 63_1. Each through hole 63_1 forms an advance port AP.

An annular recess 84_1 is formed on the inner periphery of the rotor 8, and a plurality of through holes 85_1 is formed in the rotor 8. The through holes 85_1 are arranged along the circumferential direction. FIG. 2 illustrates one through hole 85_1 out of the plurality of through holes 85_1. Each through hole 85_1 has a longitudinal direction along the radial direction. Each through hole 85_1 communicates with the corresponding one space out of a plurality of spaces each forming the advance chamber. Each through hole 85_1 communicates with the corresponding through hole 63_1 via the annular recess 84_1.

A plurality of through holes 63_2 is formed in the cylindrical wall of the center bolt 6. The through holes 63_2 are arranged along the circumferential direction. FIG. 2 illustrates two through holes 63_2 out of the plurality of through holes 63_2. Each through hole 63_2 forms a retard port RP.

An annular recess 84_2 is formed on the inner periphery of the rotor 8, and a plurality of through holes 85_2 is formed in the rotor 8. The through holes 85_2 are arranged along the circumferential direction. FIG. 2 illustrates one through hole 85_2 out of the plurality of through holes 85_2. Each through hole 85_2 has a longitudinal direction along the radial direction. Each through hole 85_2 communicates with the corresponding one space out of a plurality of spaces each forming the retard chamber. Each through hole 85_2 communicates with the corresponding through hole 63_2 via the annular recess 84_2.

An annular groove 71 is formed on the outer periphery of the spool 7. The groove 71 communicates with the supply port SP.

The state in which the supply port SP communicates with the advance port AP via the groove 71 in the valve timing adjustment device 200 is hereinafter referred to as a “first oil supply state”. In addition, the state in which the supply port SP communicates with the retard port RP via the groove 71 in the valve timing adjustment device 200 is hereinafter referred to as a “second oil supply state”.

The valve timing adjustment device 200 can be selectively set to either the first oil supply state or the second oil supply state depending on the position of the spool 7 that is linearly moving. In other words, the supply port SP can selectively communicate with either the advance port AP or the retard port RP via the groove 71 depending on the position of the spool 7 that is linearly moving. FIG. 2 illustrates the valve timing adjustment device 200 in the first oil supply state. Illustration of the valve timing adjustment device 200 in the second oil supply state is omitted.

The spool 7 has a hollow portion 72. The hollow portion 72 forms a main part of the oil exit path OEP′. One or more through holes (not illustrated) for discharging oil are formed at an end portion of the spool 7.

In the figure, SS′_1 indicates a seal surface disposed between the advance port AP and the supply port SP. The seal surface SS′_1 is a region for suppressing the occurrence of oil leakage between the advance port AP and the supply port SP. In the figure, SS′_2 indicates a seal surface disposed between the supply port SP and the retard port RP. The seal surface SS′_2 is a region for suppressing the occurrence of oil leakage between the supply port SP and the retard port RP.

The main part of the valve timing adjustment device 200 is configured as described above.

The following describes operation of the valve timing adjustment device 200, focusing on the operation of supplying oil to the advance chamber. In other words, the following mainly describes the operation in the first oil supply state.

First, oil in an oil pan is supplied to the oil supply path OSP′ by a pump. The supplied oil passes through each hole 52, each hole 53, each hole 81, each through hole 82, and the annular groove 83, and is supplied to the supply port SP. The supplied oil passes through each through hole 62 and the annular groove 71, and is supplied to the advance port AP. The supplied oil passes through each through hole 63_1, the annular recess 84_1, and each through hole 85_1, and is supplied to the advance chamber.

At the same time, at least part of oil in the retard chamber is unnecessary. The unnecessary oil passes through each through hole 85_2, the annular recess 84_2, each through hole 63_2, and the hollow portion 72, and is discharged to the oil pan. In other words, the unnecessary oil is discharged to the outside of the valve timing adjustment device 200 through the retard port RP and the oil exit path OEP′.

The following describes operation of the valve timing adjustment device 200, focusing on the operation of supplying oil to the retard chamber. In other words, the following mainly describes the operation in the second oil supply state.

First, oil in the oil pan is supplied to the oil supply path OSP′ by the pump. The supplied oil passes through each hole 52, each hole 53, each hole 81, each through hole 82, and the annular groove 83, and is supplied to the supply port SP. The supplied oil passes through each through hole 62 and the annular groove 71, and is supplied to the retard port RP. The supplied oil passes through each through hole 63_2, the annular recess 84_2, and each through hole 85_2, and is supplied to the retard chamber.

At the same time, at least part of oil in the advance chamber is unnecessary. The unnecessary oil passes through each through hole 85_1, the annular recess 84_1, each through hole 63_1, and the hollow portion 72, and is discharged to the oil pan. In other words, the unnecessary oil is discharged to the outside of the valve timing adjustment device 200 through the advance port AP and the oil exit path OEP′.

The following describes effects of the valve timing adjustment device 100.

As illustrated in FIG. 2, in the valve timing adjustment device 200, the advance port AP, the supply port SP, and the retard port RP are arranged in sequence along the axial direction. In addition, the seal surface SS′_1 is disposed between the advance port AP and the supply port SP, and the seal surface SS′_2 is disposed between the supply port SP and the retard port RP. Accordingly, in the valve timing adjustment device 200, the number of ports arranged with respect to the axial direction is three and the number of seal surfaces arranged with respect to the axial direction is two.

On the other hand, as illustrated in FIG. 1, in the valve timing adjustment device 100, the first work port WP_1 and the second work port WP_2 are arranged in sequence along the axial direction. In addition, the seal surface SS is disposed between the first work port WP_1 and the second work port WP_2. Accordingly, in the valve timing adjustment device 100, the number of ports arranged with respect to the axial direction is two and the number of seal surfaces arranged with respect to the axial direction is one. This is because of the structure in which the hole 22 disposed along the axial direction inside the cylindrical wall of the center bolt 2 is used as the oil supply path OSP. Such structure eliminates the need for a port equivalent to the supply port SP.

Thus, the valve timing adjustment device 100 achieves a reduced number of ports arranged with respect to the axial direction and a reduced number of seal surfaces arranged with respect to the axial direction, as compared with the valve timing adjustment device 200. As a result, the valve timing adjustment device 100 can be made thinner.

The following describes other effects of the valve timing adjustment device 100.

As described above, the rotor 4 is held between the flange 21 and the end portion of the camshaft 1. In other words, the rotor 4 is held by the axial force generated by the camshaft 1 and the center bolt 2. From the viewpoint of coping with such axial force, the cylindrical wall of the center bolt 2 is required to have a greater thickness. In addition, from the viewpoint of forming the hole 22 and the first annular groove 24, the cylindrical wall of the center bolt 2 is required to have a greater thickness. On the other hand, from the viewpoint of avoiding an increase in the size of the valve timing adjustment device 100 with respect to the radial direction, it is desired to avoid an increase in the outer diameter of the center bolt 2.

For these requirements, the valve timing adjustment device 100 makes it possible to avoid an increase in the outer diameter of the center bolt 2 and allow the cylindrical wall of the center bolt 2 to have a greater thickness as described below.

Specifically, the diameter of the spool 3 in the valve timing adjustment device 100 can be reduced for the following two reasons.

First, as described above, the valve timing adjustment device 100 can be made thinner than the valve timing adjustment device 200. Therefore, the axial length of the center bolt 2 can be made smaller than the axial length of the center bolt 6, and the axial length of the spool 3 can be made smaller than the axial length of the spool 7. Since the axial length of the spool 3 is smaller, the path length of the oil exit path OEP in the hollow portion 32 is smaller. Therefore, the resistance in discharging oil in the hollow portion 32 is decreased. On the basis of the amount of decrease in the resistance in discharging oil, the diameter of the spool 3 can be reduced.

Second, as described above, in the valve timing adjustment device 100, the second annular groove 31 is formed on the spool 3 and, in addition, the first annular groove 24 is formed in the center bolt 2. As a result, the resistance caused by pressure loss in such region can be decreased as compared with the case where the first annular groove 24 is not formed in the center bolt 2. On the basis of the amount of decrease in the resistance, the width of the second annular groove 31 with respect to the radial direction can be reduced. As a result, the diameter of the spool 3 can be reduced.

Here, by reducing the diameter of the spool 3, the inner diameter of the center bolt 2 can be reduced. As a result, it is made possible to avoid an increase in the outer diameter of the center bolt 2 and allow the cylindrical wall of the center bolt 2 to have a greater thickness.

The following describes other effects of the valve timing adjustment device 100.

As illustrated in FIG. 2, the valve timing adjustment device 200 has a structure in which oil is supplied to the annular groove 71 through each hole 52, each hole 53, each hole 81, each through hole 82, the annular groove 83, and each through hole 62. In other words, the valve timing adjustment device 200 has a structure in which oil is supplied to the annular groove 71 through three components (the camshaft 5, the rotor 8, and the center bolt 6).

On the other hand, as illustrated in FIG. 1, the valve timing adjustment device 100 has a structure in which oil is supplied to the second annular groove 31 through each through hole 12, the space S, each hole 22, and the first annular groove 24. In other words, the valve timing adjustment device 100 has a structure in which oil is supplied to the second annular groove 31 through two components (the camshaft 1 and the center bolt 2).

Thus, by using the valve timing adjustment device 100, the rotor 4 can be excluded from the oil supply path OSP. As a result, the number of components in the structure for oil supply can be reduced as compared with the valve timing adjustment device 200. In other words, oil supply can be achieved with a simpler structure.

As described above, the valve timing adjustment device 100 includes: the center bolt 2 being bottomed cylindrical; the spool 3 disposed in a hollow portion of the center bolt 2 so as to be linearly movable; the oil supply path OSP including a region (hole 22) that is formed inside the cylindrical wall of the center bolt 2 and along the longitudinal direction (axial direction) of the center bolt; the first annular groove 24 formed on the inner periphery of the center bolt 2 and communicating with the oil supply path OSP; and the second annular groove 31 formed on the outer periphery of the spool 3, disposed to face the first annular groove 24, and communicating with the oil supply path OSP via the first annular groove 24, in which the oil supply path OSP is capable of selectively communicating with either the first work port WP_1 or the second work port WP_2 via the first annular groove 24 and the second annular groove 31 depending on the position of the spool 3 that is linearly moving. Thus, the need for a port equivalent to the supply port can be eliminated. As a result, the number of ports arranged with respect to the axial direction can be reduced and the number of seal surfaces arranged with respect to the axial direction can be reduced. Therefore, the valve timing adjustment device 100 can be made thinner. In addition, an increase in the outer diameter of the center bolt 2 can be avoided. Furthermore, oil supply can be achieved with a simpler structure.

Second Embodiment

FIG. 3 is an explanatory diagram illustrating a main part of a valve timing adjustment device according to a second embodiment. Referring to FIG. 3, the following describes the valve timing adjustment device according to the second embodiment. In FIG. 3, components similar to those shown in FIG. 1 are given the same reference numerals and description thereof is omitted.

As illustrated in FIG. 3, an end portion of a camshaft 1, a center bolt 2 a, a spool 3, and a rotor 4 a form the main part of a valve timing adjustment device 100 a.

An annular groove (hereinafter referred to as a “third annular groove”) 25_1 is formed on the outer periphery of the center bolt 2 a. Each through hole 23_1 communicates with the corresponding through hole 42_1 via the third annular groove 25_1. Forming the third annular groove 25_1 achieves the state in which each through hole 23_1 communicates with the corresponding through hole 42_1 regardless of the positional relationship between the center bolt 2 a and the rotor 4 a with respect to the rotation direction.

Specifically, in the valve timing adjustment device 100, the annular recess 41_1 is formed on the inner periphery of the rotor 4 and at a position corresponding to the first work port WP_1 (see FIG. 1). On the other hand, in the valve timing adjustment device 100 a, the third annular groove 25_1 is formed on the outer periphery of the center bolt 2 a and at a position corresponding to the first work port WP_1 (see FIG. 3).

An annular groove (hereinafter referred to as a “fourth annular groove”) 25_2 is formed on the outer periphery of the center bolt 2 a. Each through hole 23_2 communicates with the corresponding through hole 42_2 via the fourth annular groove 25_2. Forming the fourth annular groove 25_2 achieves the state in which each through hole 23_2 communicates with the corresponding through hole 42_2 regardless of the positional relationship between the center bolt 2 a and the rotor 4 a with respect to the rotation direction.

Specifically, in the valve timing adjustment device 100, the annular recess 41_2 is formed on the inner periphery of the rotor 4 and at a position corresponding to the second work port WP_2 (see FIG. 1). On the other hand, in the valve timing adjustment device 100 a, the fourth annular groove 25_2 is formed on the outer periphery of the center bolt 2 a and at a position corresponding to the second work port WP_2 (see FIG. 3).

The main part of the valve timing adjustment device 100 a is configured as described above.

Operation of the valve timing adjustment device 100 a is similar to that of the valve timing adjustment device 100. Therefore, description thereof is omitted.

The following describes effects of the valve timing adjustment device 100 a.

As described in the first embodiment, the rotor 4 a is held by the axial force generated by the camshaft 1 and the center bolt 2 a. From the viewpoint of coping with such axial force, each of the contact surfaces CS_1 and CS_2 is required to have an area (hereinafter referred to as a “contact area”) equal to or greater than a predetermined value.

Here, the valve timing adjustment device 100 has a structure in which the annular recesses 41_1 and 41_2 are formed on the inner periphery of the rotor 4. In order to increase the contact area in such structure, the flange 21 is required to have a larger diameter and the end portion of the camshaft 1 is required to have a larger diameter. As a result, there arises the problem of a larger size of the valve timing adjustment device 100 with respect to the radial direction.

On the other hand, in the valve timing adjustment device 100 a, the third annular groove 25_1 and the fourth annular groove 25_2 are arranged on the outer periphery of the center bolt 2 a. Thus, the need for a recess equivalent to the recess 41_1 and a recess equivalent to the recess 41_2 can be eliminated. As a result, the area of the contact surface CS_1 can be made larger without increasing the diameter of the flange 21. In addition, the area of the contact surface CS_2 can be made larger without increasing the diameter of the end portion of the camshaft 1. In other words, the valve timing adjustment device 100 a can be made smaller in size with respect to the radial direction.

Note that, as described in the first embodiment, the cylindrical wall of the center bolt 2 (that is, the cylindrical wall of the center bolt 2 a) is thicker than the cylindrical wall of the center bolt 6. In other words, the cylindrical wall of the center bolt 6 is thinner than the cylindrical wall of the center bolt 2 (that is, the cylindrical wall of the center bolt 2 a). Therefore, assuming that a groove similar to the third annular groove 25_1 and a groove similar to the fourth annular groove 25_2 are formed on the outer periphery of the center bolt 6, there is a possibility that the axial force for holding the rotor 8 cannot be coped with due to insufficient strength of the cylindrical wall of the center bolt 6.

On the other hand, the center bolt 2 (that is, the center bolt 2 a) having such a thicker cylindrical wall is capable of achieving sufficient strength to cope with the axial force for holding the rotor 4 a in spite of the fact that the third annular groove 25_1 and the fourth annular groove 25_2 are formed. Thus, a structure having the third annular groove 25_1 and the fourth annular groove 25_2 can be established.

The following describes modifications of the valve timing adjustment device 100 a.

It is possible not to form the third annular groove 25_1 on the center bolt 2 a but to form a recess similar to the recess 41_1 on the rotor 4 a. In this case, the area of the contact surface CS_2 can still be made larger without increasing the diameter of the end portion of the camshaft 1.

Alternatively, it is possible not to form the fourth annular groove 25_2 on the center bolt 2 a but to form a recess similar to the recess 41_2 on the rotor 4 a. In this case, the area of the contact surface CS_1 can still be made larger without increasing the diameter of the flange 21.

Note that, however, from the viewpoint of reducing the size of the valve timing adjustment device 100 a with respect to the radial direction, it is more preferred that the third annular groove 25_1 is formed on the center bolt 2 a and the fourth annular groove 25_2 is formed on the center bolt 2 a as described above.

As described above, the valve timing adjustment device 100 a includes the third annular groove 25_1 formed on the outer periphery of the center bolt 2 a and at a position corresponding to the first work port WP 1. As a result, the area of the contact surface CS_1 can be made larger without increasing the diameter of the flange 21.

In addition, the valve timing adjustment device 100 a includes the fourth annular groove 25_2 formed on the outer periphery of the center bolt 2 a and at a position corresponding to the second work port WP_2. As a result, the area of the contact surface CS_2 can be made larger without increasing the diameter of the end portion of the camshaft 1.

Within the scope of the present invention, individual embodiments of the present invention may be freely combined, any component of the individual embodiments may be modified, or any component of the individual embodiments may be omitted.

INDUSTRIAL APPLICABILITY

The valve timing adjustment device of the present invention can be used for VVT.

REFERENCE SIGNS LIST

1: camshaft, 2, 2 a: center bolt, 3: spool, 4, 4 a: rotor, 5: camshaft, 6: center bolt, 7: spool, 8: rotor, 11: recess, 12: through hole, 21: flange, 22: hole, 23_1: through hole, 23_2: through hole, 24: groove (first annular groove), 25_1: groove (third annular groove), 25_2: groove (fourth annular groove), 31: groove (second annular groove), 32: hollow portion, 41_1: recess, 41_2: recess, 42_1: through hole, 42_2: through hole, 51: recess, 52: hole, 53: hole, 61: flange, 62: through hole, 63_1: through hole, 63_2: through hole, 71: groove, 72: hollow portion, 81: hole, 82: through hole, 83: groove, 84_1: recess, 84_2: recess, 85_1: through hole, 85_2: through hole, 100, 100 a: valve timing adjustment device, 200: valve timing adjustment device 

1. A valve timing adjustment device comprising; a center bolt being bottomed cylindrical; a spool disposed in a hollow portion of the center bolt so as to be linearly movable; an oil supply path including a region that is formed inside a cylindrical wall of the center bolt and along a longitudinal direction of the center bolt; a first annular groove formed on an inner periphery of the center bolt and communicating with the oil supply path; and a second annular groove formed on an outer periphery of the spool, disposed to face the first annular groove, and communicating with the oil supply path via the first annular groove, wherein the oil supply path is capable of selectively communicating with either a first work port or a second work port via the first annular groove and the second annular groove depending on a position of the spool that is linearly moving.
 2. The valve timing adjustment device according to claim 1, further comprising a third annular groove formed on an outer periphery of the center bolt and at a position corresponding to the first work port.
 3. The valve timing adjustment device according to claim 1, further comprising a fourth annular groove formed on an outer periphery of the center bolt and at a position corresponding to the second work port.
 4. The valve timing adjustment device according to claim 2, further comprising a fourth annular groove formed on an outer periphery of the center bolt and at a position corresponding to the second work port. 